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282 PATHOLOGY OF THE HARD TISSUES OF THE TEETH.

Apical space. The space between the bone, or wall of the alveolus, and the apex
of the root of a tooth. This space is filled with the soft tissues of the peridental mem-
brane, and is the seat of alveolar abscess.
Approximate. Next to, nearest to. To draw near to. Occasionally employed to
designate the distal or mesial surface of a tooth. See Proximal.
Arch. An arc or portion of a circle. Any object in nature or art which is curved,
like an arc. The dental arch, the arrangement of the teeth in a bow shape or arc.
Aseptic. The condition of freedom from sepsis or freedom from microorganisms
which might possibly produce a condition of sepsis.
Aseptic operating. To make the conditions such as to prevent the entrance of
microorganisms during an operation.
Aseptic wound. A wound not infected with microorganisms.
Asphyxia. Suspended animation from suffocation.
Atrophy. ' Latin, Atrophia, without nourishment. A, without ; trophia, nour-
'
ishment. ' '—Webster.
A result of defect of, or a failure of, nutrition of a part which limits its forma-
tion. A diminution of the size of a part, or a wasting due to defective nutrition.
Of the teeth: a failure in the formation of certain parts of the enamel and dentin
because of a failure of nutrition at the time those particular parts should have been
formed. This results in a dwarfing of certain parts of the tooth and causes it to be
malformed.
A wasting of certain parts or organs of the body because of disease affecting
the trophic nerves, tinder conditions on non-use of muscles frpm disease or accident
they waste away from lack of nutrition. The term atrophy is applied to many condi-
tions characterized by wasting of parts due to disease of the trophic nerves supplying
the part and consequent failure of nutrition. Syn. Hypoplasia.
Atrophy marks. The peculiar marks left on the teeth by reason of a failure of
nutrition during their development.
Axial. Pertaining to the long axis of a tooth. See Axial Surface.
Axial angles of teeth. The line angles that are parallel with the long axes of
the teeth are called axial angles. They are the mesio-buccal and mesio-labial, disto-
buccal and disto-labial, mesio-lingual and disto-lingual angles.
Axial cavities. Cavities beginning in any of the axial surfaces of the teeth; as
the mesial, buccal or labial, distal and lingual surfaces.
Axial surfaces. Those surfaces of the teeth that are parallel with their long
axes. They are labial or buccal, lingual, mesial and distal surfaces.
Axial wall of cavities. A cavity wall that is parallel with the long axis of a
tooth and covers the pulp chamber, is called the axial wall.
Axial walls of pulp chambers. Those walls that are parallel with the long axes
of the teeth; the mesial, distal, buccal and lingual walls.
Ajcio-bucco-lingual plane. A plane passing through any part of a tooth from
buccal to lingual parallel with its long axis. See Figure 11, Vol. 2.
Axio-labio-lingual plane. A plane passing through any part of an incisor or
cuspid tooth from labial to lingual parallel with its long axis.
Axio-mesio-distal plane. A plane passing through any part of a tooth mesio-
distally parallel with its long axis. See also Mesio-distal Plane. See Figure 10, Vol. 2.
Bacillus. (PI. Bacilli.) A rod-shaped bacterium.
Bacteria. A class of microscopic fungi destitute of chlorophyl. They follow
more or less closely four forms: (1) the sphere, (2) the rod, (3) the spirilla, (4)